It is known that non-coordinating ion-containing compounds can be used as cocatalyst components for metallocene catalysts and, for example, Japanese International Application Domestic Publication No. 1-502036 discloses production of olefin polymers with high polymer activity without the use of methylaluminoxane. Such catalyst systems, however, have poor stability and exhibit reduced activity when stored after their preparation, and they must therefore be used promptly after preparation.
One attempt at preventing reduction in activity after catalyst preparation has been to add a hydrocarbon compound which is inert with respect to the metallocene catalyst, as proposed in Japanese Unexamined Patent Publication No. 11-246614. This publication specifically discloses only methylaluminoxane as the cocatalyst component of the metallocene catalyst, and does not disclose the effect of using a non-coordinating ion-containing compound. According to the method described therein, it is difficult to prevent reduction in polymerization activity when using a non-coordinating ion-containing compound as the cocatalyst.
International Publication WO96/34020 discloses a catalyst comprising a metallocene compound, a non-coordinating ion-containing compound and a hydrocarbon compound which is inert with respect to the metallocene catalyst. The stability of the catalyst is not discussed in this publication, and again, it is difficult to prevent reduction in polymerization activity after preparation of the catalyst, while other problems arise in the case of olefin polymers, and particularly propylene polymer, including an increased content of solvent-soluble components and often a wider molecular weight distribution.
Thus, as a reduction in polymerization activity cannot be prevented simply by using an inert hydrocarbon in systems employing non-coordinating ion-containing compounds as cocatalysts, the aforementioned problems of such catalyst systems remain unsolved.
On the other hand, in publications such as International Publication W096/41808 and Japanese International Application Domestic Publication No. 7-501573, there have been proposed olefin polymerization catalysts comprising a cocatalyst component wherein a non-coordinating ion-containing compound is chemically bonded to a fine particulate carrier, together with a metallocene compound and organic aluminum. However, such catalysts or cocatalysts undergo considerable alteration after preparation and exhibit reduced polymerization activity after storage and, thus, using such a stored catalyst or cocatalyst to produce an olefin polymer, and particularly a propylene polymer, results in increased content of the solvent-soluble component and a wider molecular weight distribution.